The family was wealthy, and young Francis grew up quite vain and
utterly devoted to worldly pleasures. His friends referred to him
as il damerino ("the ladies' man"). Then, while he
was attending school at the Jesuit college at Spoleto, he fell
dangerously ill. He promised that if he recovered, he would enter
religious life. Upon his recovery, however, he did not act
immediately upon his promise.

One day he saw a picture of the Sorrowful Mother carried in a
procession. To Francis, it seemed that she was looking straight at
him. At the same time, he heard a voice in his heart telling him,
"Francis, the world is not for you anymore."

A year or two later, when he fell ill again, he renewed his
promise. Again he recovered. This time he fulfilled his vow,
astonishing everyone when he announced that he was entering the
Passionist Order immediately after his graduation in 1856. It was
there that he took the name Gabriel.

Within the Passionist community, he spent his remaining years in
prayer, study, and reflection. He was quite devoted to Mary, the
Mother of God, because of his vision and also perhaps partly because
he had lost his own mother at the age of four.

Another story about Gabriel involves a group of soldiers who were terrorizing the town of Isola. Friar Possenti approached them
and asked them to leave. When they refused, he drew a pair of
pistols from underneath his robes. Or maybe, as some sources say,
he took the pistols from one of the bullies. Either way, they laughed at
him, thinking that a priest was unlikely to be much of a marksman. Gabriel took aim at a lizard across the road, and cut it in half with a well-placed shot. Then he pointed out that he still had a shot left in his other pistol, and he asked which of the men wanted it. The men left. This story is used by some as an argument for his adoption as the patron saint of handgunners.